Corporate Information

At 7:15am, Mar 15th, Unit 4 achieved reactor cold shutdown. Accordingly,
all the units in Fukushima Daini Nuclear Power Station have achieved
reactor cold shutdown.
Unit 1 (shut down at 2:48pm on Mar 11th)
- Reactor is shut down and reactor water level is stable.
- Offsite power is available.
- At 8:19am, Mar 12th, there was an alarm indicating that one of the
control rods was not properly inserted, however, at 10:43am, Mar 12th
the alarm was spontaneously called off. Other control rods has been
confirmed that they are fully inserted (reactor is in subcritical status)
- Status of main steam isolation valve: closed
- We do not believe there is leakage of reactor coolant in the
containment vessel at this moment.
- At 5:22am, Mar 12th, the temperature of the suppression chamber
exceeded 100 degrees. As the reactor pressure suppression function was
lost, at 5:22am, Mar 12th, it was determined that a specific incident
stipulated in article 15, clause 1 has occurred.
- We decided to prepare implementing measures to reduce the pressure of
the reactor containment vessel (partial discharge of air containing
radioactive materials) in order to fully secure safety. This preparation
work started at around 9:43am, Mar 12th and finished at 6:30pm, Mar 12th.
- Restoration work in reactor cooling function that was conducted to
achieve reactor cold shutdown has been completed and cooling of the
reactor has been commenced at 1:24 am, Mar 14th.
- At 10:15am, Mar 14th, it has been confirmed that the average water
temperature of the suppression chamber has continuously fell bellow 100
degrees.
- At present, the unit has achieved reactor cold shutdown.
Unit 2 (shut down at 2:48pm on Mar 11th)
- Reactor is shut down and reactor water level is stable.
- Offsite power is available.
- Control rods are fully inserted (reactor is in subcritical status)
- Status of main steam isolation valve: closed
- We do not believe there is leakage of reactor coolant in the
containment vessel.
- At 5:32am, Mar 12th, the temperature of the suppression chamber
exceeded 100 degrees. As the reactor pressure suppression function was
lost, at 5:32am, Mar 12th, it was determined that a specific incident
stipulated in article 15, clause 1 has occurred.
- We decided to prepare implementing measures to reduce the pressure of
the reactor containment vessel (partial discharge of air containing
radioactive materials) in order to fully secure safety. This preparation
work started at around 10:33am, Mar 12th and finished at 10:58pm, Mar
12th.
- Restoration work in reactor cooling function that was conducted to
achieve reactor cold shutdown has been completed and cooling of the
reactor has been commenced at 7:13 am, Mar 14th.
- At 3:52pm, Mar 14th, it has been confirmed that the average water
temperature of the suppression chamber has continuously fell bellow 100
degrees.
- At present, the unit has achieved reactor cold shutdown.
Unit 3 (shut down at 2:48pm on March 11th)
- Reactor is shut down and reactor water level is stable.
- Offsite power is available.
- Control rods are fully inserted (reactor is in subcritical status)
- Status of main steam isolation valve: closed
- We do not believe there is leakage of reactor coolant in the
containment vessel.
- We decided to prepare implementing measures to reduce the pressure of
the reactor containment vessel (partial discharge of air containing
radioactive materials) in order to fully secure safety. The preparation
woke started at around 12:08pm, Mar 12th and finished at 12:13pm, Mar
12th.
- At present, the unit has achieved reactor cold shutdown.
Unit 4 (shut down at 2:48pm on March 11th)
- Reactor is shut down and reactor water level is stable.
- Offsite power is available.
- At 0:43pm, Mar 13th, there was a signal indicating that one of the
control rods may have not properly inserted. However, we confirmed that
it was inserted completely by another signal. We will inspect the reason
of this.
- Status of main steam isolation valve: closed
- We do not believe there is leakage of reactor coolant in the
containment vessel.
- In order to cool down the reactor, injection of water into the reactor
had been done by the Reactor Core Isolation Cooling System, however,
At 6:07am, Mar 12th, the temperature of the suppression chamber exceeded
100 degrees. As the reactor pressure suppression function was lost,
at 6:07am, Mar 12th, it was determined that a specific incident
stipulated in article 15, clause 1 has occurred.
- We decided to prepare implementing measures to reduce the pressure of
the reactor containment vessel (partial discharge of air containing
radioactive materials) in order to fully secure safety. The preparation
woke started at around 11:44am, Mar 12th and finished at around 11:52am,
Mar 12th.
- Restoration work in reactor cooling function that was conducted to
achieve reactor cold shutdown has been completed and cooling of the
reactor has been commenced at 3:42 pm, Mar 14th.
- At 7:15pm, Mar 15th, it has been confirmed that the average water
temperature of the suppression chamber has continuously fell bellow 100
degrees.
- At present, the unit has achieved reactor cold shutdown.
- At approximately 11:01am, Mar 14th, an explosion followed by white
smoke occurred at the reactor building of Unit 3. It was believed to be
a hydrogen explosion.
- There was an increase of radiation dose at site boundary measured at
the monitoring post of Fukushima Daini Nuclear Power Station.
Accordingly, at 10:07pm Mar 14th and at 12:35am Mar 15th, it was
determined that that a specific incident stipulated in article 10,
clause 1 (Increase of radiation dose at site boundary) has occurred.
- We will continue to monitor in detail the possibility of radioactive
material being discharged from exhaust stack or discharge canal.